JP2000113915A - Aluminum wire connection structure and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion of an aluminum wire in a connection part in a connection structure connecting an aluminum wire to a connected body together via an anisotropic conductive material. SOLUTION: A positive electrode base board 3 in an envelope 2 for a fluorescent character display tube 1 is protruded from a box-shaped outline. Wiring such as an electrode inside the envelope 2 is pulled out to the surface of one end part 3a in the positive electrode base board 3 so as to constitute an external terminal part 5 of an aluminum film. The external terminal part 5 is covered with a protection film 7 connected to a cloth layer 6 serving as an insulating film inside the envelope 2. To the end part of the external terminal part 5, a flexible cable 8 is connected via an anisotropic conductive material 9 (ACF) by thermo-compression bonding. The protection film 7 is formed so as to be provided with a length long enough to penetrate the lower side of the cable 8. The connection part is covered with a molding material. Although a protruded part 9a of the anisotropic conductive material 9 including chloride ions corroding aluminum is hardened insufficiently, no corrosion is caused because the aluminum external terminal part 5 beneath the protruded part 9a is covered with the protection film 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring connection structure particularly useful for connecting a flexible connection wiring or the like with an anisotropic conductive material to an aluminum wiring formed on a substrate, and a method of manufacturing the same. About the method.

[0002]

2. Description of the Related Art FIG. 4 shows an external terminal 101 of a fluorescent display tube 100 and a flexible cable 102 as an external wiring.
An example of a connection structure in which the anisotropic conductive material 103 (ACF) is connected therebetween is shown.

[0003] Generally, the fluorescent display tube 100 has a box-shaped envelope formed by airtightly assembling a plate made of an insulating material such as glass with a sealing material. An anode, a light emitting display unit having a phosphor layer, a cathode as an electron source, a control electrode for controlling electrons, and the like are accommodated therein. On the inner surface of the anode substrate 104 forming a part of the envelope, wiring conductors of the internal electrodes including the anode are routed. Then, the wiring conductor is airtightly penetrated through the sealing portion of the envelope, and is drawn out to the surface of the anode substrate 104 outside the envelope, thereby forming the external terminal portion 101. Usually, a large number of the external terminal portions 101 are arranged on the anode substrate outside the envelope at a fine pitch, and since the width thereof is considerably small, the resistance is often increased. Therefore, it is sometimes difficult to use a high-resistance conductive material such as ITO (Indium Tin Oxide), and generally, an aluminum thin film is often used. The wiring inside the envelope and a part of the external terminals outside the envelope are covered with a cloth 105.

When the fluorescent display tube 100 is connected to a driving circuit (not shown) provided outside, a flexible cable 102 as shown in FIG. 4 may be used. This flexible cable 102 is commonly called TAB, and has a C film on one side of a polyimide film 106 as a base material.
The u wiring 107 is formed. Cu wiring 107
The pitch corresponding to the pitch of the external terminal portion 101 of the fluorescent display tube 100 to be connected is selected.

The external terminal 101 of the fluorescent display tube 100
And the anisotropic conductive material 103 (ACF) connecting the wiring 107 of the flexible cable 102 is made by dispersing conductive particles in a thermosetting adhesive such as an epoxy-based adhesive, and is usually in the form of a sheet. Supplied as conductive material. The anisotropic conductive material 103 is placed on the external terminal portion 101 of the fluorescent display tube 100, the wiring 107 of the flexible cable 102 is positioned therefrom, and these are thermocompressed.

The anisotropic conductive material 103 has high conductivity in the thickness direction because the adhesive is melted by heating and pressing, and the dispersed conductive particles are trapped between the opposing electrodes. In the plane direction, the conductive particles are dispersed to such an extent that they do not come into contact with each other, and the adhesive becomes non-conductive, so that high insulation properties can be obtained. The mechanical connection between the conductive particles and the electrodes is obtained by an adhesive. For this reason, the many external terminal portions 101 of the fluorescent display tube 100 are electrically connected only to the respective wires 107 of the flexible cable 102 positioned with respect to these, and the external terminal portion 101 and the flexible cable 102 It is securely connected mechanically.

The connection between the external terminal 101 and the flexible cable 102 is covered with a molding material 108 such as a resin for the purpose of waterproofing or the like.

[0008]

In the conventional connection structure described above, when the external terminal portion 101 of the fluorescent display tube 100 and the flexible cable 102 are thermocompressed with the anisotropic conductive material 103 interposed therebetween, the anisotropic conductive Since the epoxy resin contained in the material 103 has fluidity, the anisotropic conductive material 103 protrudes from between them, and comes out onto the external terminals 101 not facing the flexible cable 102. Then, there has been a problem that a part 110 of the aluminum external terminal portion 101 in contact with the protruding anisotropic conductive material 103 is corroded.

The present inventors have conducted intensive studies on the cause of this corrosion, and have obtained the following findings. First, an epoxy resin as an adhesive for the anisotropic conductive material 103 contains hydrolyzable chlorine. At the portion sandwiched between the external terminal portion 101 and the flexible cable 102, the epoxy resin is cured by thermocompression bonding, so that chlorine cannot be taken into the network structure of the cured product and move.
Opportunity to react with aluminum. However, in the protruding anisotropic conductive material 103, the curing reaction by thermocompression bonding is incomplete, so that chlorine ions approach the aluminum of the external terminal portion 101 and destroy the aluminum oxide film. When the fluorescent display tube 100 is driven, a potential difference between the external terminal portion 101 and the wiring of the flexible cable 102 and a long-term effect of moisture contained in the molding material cause an electrochemical reaction to occur and the external terminal portion 101
Corrosion of aluminum progresses.

The present invention has been made based on the above-mentioned knowledge of the inventor to solve the above-mentioned problem of aluminum wiring corrosion. In this invention, the aluminum wiring and the connected body are made of an anisotropic conductive material. In the connection structure to connect,
The purpose is to prevent corrosion of the aluminum wiring at the connection portion.

[0011]

According to a first aspect of the present invention, there is provided a connection structure for an aluminum wiring, comprising: an aluminum wiring (external terminal portion) formed on a substrate (anode substrate); In an aluminum wiring connection structure for connecting a body (cable 8) with an anisotropic conductive material (9), the connection protrudes from between the aluminum wiring (external terminal portion 5) and the connected body (cable 8). At least the connected object (cable 8) so that the anisotropic conductive material (9a) does not contact the aluminum wiring (external terminal portion 5) not facing the connected object (cable 8).
, The aluminum wiring (external terminal portion 5) not facing the connected object (cable 8) is covered with a protective film (7).

According to a second aspect of the present invention, an aluminum wiring (external terminal portion 5) formed on a substrate (anode substrate 3) of the fluorescent display tube (1) and the aluminum wiring outside the fluorescent display tube. Connection wiring (cable 8) using an anisotropic conductive material (9), in the aluminum wiring connection structure, between the aluminum wiring (external terminal portion 5) and the connection wiring (cable 8). At least in the vicinity of the connection wiring (cable 8), the protruding anisotropic conductive material (9a) is prevented from contacting the aluminum wiring (external terminal portion 5) not facing the connection wiring (cable 8). The aluminum wiring (external terminal portion 5) not facing the connection wiring (cable 8) is covered with a protective film (7).

According to a third aspect of the present invention, in the connection structure for an aluminum wiring according to the first or second aspect, the protective film (7) is made of a lead oxide glass.

According to a fourth aspect of the present invention, in the connection structure for an aluminum wiring according to the first or second or third aspect, the anisotropic conductive material (9) comprises a large number of fine conductive particles. It is characterized by being an epoxy adhesive containing.

According to the above structure, even if the anisotropic conductive material (9) protrudes from between the aluminum wiring (5) and the external connected body (connection wiring) (8), the protruding portion. Since the aluminum wiring (5) is covered with the protective film (7), it does not corrode.

According to a fifth aspect of the present invention, there is provided a method for connecting an aluminum wiring (external terminal portion 5) having an end portion covered with a protective film (7) using an anisotropic conductive material (9). This is a method of connecting to a connection body (cable 8). The feature is that the end of the connected body (cable 8) is connected to the aluminum wiring (external terminal 5) with the anisotropic conductive material (9) in between.
And an elastic pressing member (silicone sheet 2) that is thicker than the protective film (7) and overlaps with the end of the protective film (7).
In 3), the end of the connected object (cable 8) is pressed while being heated.

At the exposed end of the aluminum wiring (external terminal portion 5), the protective film (7) forms a step, but according to the above method, an elastic pressing material (silicon sheet 23) is used. Since it can be deformed in accordance with the step, a sufficient pressure is applied to the anisotropic conductive material (9) to crush the conductive particles in the anisotropic conductive material (9) and secure a sufficient electrical connection. can do.

[0018]

FIG. 1 shows an example of an embodiment of the present invention.
This will be described with reference to FIG. First, the connection structure of the present embodiment will be described with reference to FIGS.

As shown in FIG. 1, the fluorescent display tube 1 is provided with a box-shaped envelope 2 which is made of a plate made of an insulating material such as glass and hermetically assembled with a sealing material. One end 3 a of the anode substrate 3 that constitutes a part of the envelope 2 protrudes from the box-shaped outer shape of the envelope 2. Inside the envelope 2, an anode formed by attaching a phosphor layer on an anode conductor, a cathode serving as an electron source, a control electrode for controlling electrons, and the like are housed. The wiring conductor 4 made of an aluminum film connected to these electrodes is drawn out to the surface of the one end 3a of the anode substrate 3 outside the envelope 2 through the sealing portion of the envelope 2 in an airtight manner. And the external terminal portion 5 made of an aluminum film. The number of the external terminal portions 5 corresponding to the number of electrodes and the structure in the envelope 2 is arranged at a predetermined pitch. These wiring conductors 4 and external terminal portions 5 are manufactured in the same process.

The wiring conductor 4 in the envelope 2 is covered with a cross layer 6 as an insulating layer made of lead oxide glass, for example, lead borosilicate glass. The insulating layer constituting the cloth layer 6 may contain a pigment in order to prevent reflection of external light or the like. The cross layer 6 is continuously formed outside the envelope 2 as a protective film 7 for the external terminal portion 5 outside the envelope 2. That is, the protective film 7 covers portions other than the connection portions at the ends of the external terminal portions 5. Cloth layer 6 in envelope 2
And the protective film 7 of the external terminal portion 5 are the same and can be manufactured in the same process.

A flexible cable 8 is connected to an end of the external terminal 5 not covered with the protective film 7 by an anisotropic conductive material 9 (AC
F) and are connected by thermocompression bonding. The flexible cable 8 (TAB) is one in which a Cu wiring 11 is formed on one surface of a polyimide film 10 as a base material.
The pitch of the Cu wiring 11 is selected so as to correspond to the pitch of the external terminals 5 of the fluorescent display tube 1 to be connected. The anisotropic conductive material 9 is a sheet-like material in which conductive particles are dispersed in a thermosetting adhesive such as an epoxy-based material. Although not shown, the other end of the cable 8 is connected to a drive circuit or a connection portion such as a printed circuit board on which the drive circuit is mounted.

As shown in FIG. 1, the anisotropic conductive material 9 protrudes from between the cable 8 and the external terminal portion 5 in the process of thermocompression bonding. Are covered with a protective film 7. That is, the protective film 7 is formed of at least the protruding anisotropic conductive material 9
It is necessary to cover the external terminal portion 5 provided below the a. Alternatively, the protective film 7 is formed to have a length such that the protective film 7 extends under the cable 8. As shown, assuming that the distance between the tip of the wiring 11 of the cable 8 and the tip of the external terminal portion 5 is a and that the distance between the tip of the wiring 11 of the cable 8 and the tip of the protective film 7 is b, (b / a) = 0.
1 to 0.15 is appropriate.

As a specific numerical example, a = 2.0 m
For m, b = 0.2 to 0.3 mm is an appropriate value.
Increasing the dimension of “b” is because the protruding anisotropic conductive material 9
Although it is preferable in terms of preventing aluminum from being corroded by a, the size (ab) of the portion for electrically connecting the wiring 11 of the cable 8 and the external terminal portion 5 is shortened, so that there is a problem that the connection resistance increases. . Therefore, in order to prevent corrosion of aluminum and to ensure appropriate connection resistance, the above-described size range is preferable.

As shown in FIG. 2, the thickness of the protective film 7 must be large enough to cover the external terminals 5 arranged at a predetermined interval. Generally, the thickness of the aluminum thin film used for wiring in the fluorescent display tube 1 is 1.2 μm.
The thickness of the cloth layer 6 made of lead borosilicate glass is sufficiently larger than this, and there is no problem. In this example, the thickness of the protective film 7 (cross layer 6) is about 15 to 20 μm.

According to the structure of this embodiment in which the protective film 7 covers the external terminal portion 5, the aluminum film of the external terminal portion 5 is merely protected from corrosion as long as the present fluorescent display tube is generally used. Moisture proof is sufficiently ensured. However, if the connection between the external terminal 5 and the cable 8 is covered with a molding material such as a resin, a high moisture-proof property can be obtained even in a special environment with high humidity.

In the present invention, the fluorescent display tube is not only a display element that emits a segment of a fixed pattern, but also a fluorescent light emitting element that selectively drives a display section of a fine matrix pattern to perform desired character display and graphic display. Including tubes. Normally, in the latter graphic fluorescent light emitting tube, the anode, which is the light emitting portion, is divided into fine patterns, and the number of wiring conductors routed therefrom is large, and therefore the number of external terminals drawn out is large. For example, in the case of an A4 size (emission width 210 mm), 300 dpi fluorescent tube, the total number of dots is about 2500, and the pitch of wiring drawn out on both sides of the envelope is about 0.17 mm. Very fine and dense compared to the display tube wiring.

The wiring drawn out on both sides of the envelope is connected to the TAB as described above, but by further reducing the wiring pitch and increasing the density, the outer shape of the TAB can be reduced. Reducing TAB means that a smaller polyimide film 10 can be used as the base material, which increases the number of substrates.
This leads to a reduction in the unit price of AB.

In the above situation, the actual wiring pitch of the external terminal of the fluorescent tube to which the structure of this embodiment is applied is, for example, 110 μm. As described above, since the corrosion of the wiring is electrochemically generated, the lifetime of the corrosion becomes shorter as the electric field intensity becomes stronger. When the wiring pitch becomes smaller, the electric field strength between the wirings becomes stronger, so that wiring corrosion is more likely to occur.

Therefore, if the research and development of the fluorescent arc tube proceeds in the direction of higher resolution, the wiring pitch of the external terminal portion becomes smaller, and the corrosion problem becomes more serious. Becomes very important.

Next, a process of connecting the external terminal 5 and the cable 8 in this embodiment will be described with reference to FIG. FIG.
In the figure, reference numeral 20 denotes a thermocompression bonding device used for thermocompression bonding using the anisotropic conductive material 9 described above. The thermocompression bonding apparatus 20 includes an air cylinder 21 as a pressing unit, and a heater head 22 as a heating unit provided at a tip of a rod of the air cylinder 21. The contact surface of the heater head 22 is provided with a silicon sheet 23 as a cushion material. The silicon sheet 23 of this example has a thickness of 200 μm.
m.

An anisotropic conductive material 9 is placed on the external terminal 5 of the fluorescent display tube 1, and the wiring 1 of the flexible cable 8 is placed therefrom.
1 are positioned and pressed while being heated by the thermocompression bonding device 20. The Cu wiring 11 of the cable 8 and the external terminal portion 5 (Al) are electrically and mechanically connected by the anisotropic conductive material 9 which has been melt-hardened.

At this time, the conductive particles (for example, metal balls having a diameter of about 5 μm) in the anisotropic conductive material 9
The two wirings are electrically connected by being crushed between the u wiring 11 and the external terminal portion 5 (Al). For example, if the conductive particles are metal balls having a diameter of about 5 μm, the conductive particles are crushed to a thickness of about 2 μm and are electrically conducted.

As described above, the thickness of the protective film 7 is 15 to 2
0 μm, and as shown in FIG.
When pressure is applied in step 2, the protective film 7 becomes a step, and it may be difficult to crush the conductive particles in the anisotropic conductive material 9. However, in this example, since the thickness of the protective film 7 is sufficient (about 200 μm) and the elastic silicon sheet 23 is provided on the heater head 22, the silicon sheet 23 with high elasticity can be formed. By deforming according to the step, the step is absorbed, and sufficient pressure can be applied to the anisotropic conductive material 9 to crush the conductive particles.
The silicon sheet 23 has sufficient heat resistance.

In this embodiment, the silicon sheet 23 having a thickness of about 200 μm is used.
A Teflon sheet having a thickness of about μm can be used.

According to the steps described above, the fluorescent display tube 1
Are electrically connected only to the respective wirings 11 of the flexible cable 8 positioned with respect to these, and the external terminal 5 and the flexible cable 8 are securely connected mechanically. Is done.

After that, the external terminal 5 and the flexible cable 8
May be covered with a molding material such as a resin in order to further ensure functions such as waterproofing.

As described above, according to the connection structure of this embodiment, the external terminal portion 5 made of aluminum is covered with the protective film 7 made of lead borosilicate glass having excellent moisture permeability, and is used for connection with the external cable 8. Since the anisotropic conductive material 9 was protected from protrusion, the inconvenience of corrosion of the aluminum of the external terminal portion 5 at the connection portion was eliminated.

Further, according to the connection method of this embodiment, since the silicon sheet 23 can be deformed corresponding to the step of the protective film 7 at the end of the aluminum wiring, sufficient pressure is applied to the anisotropic conductive material 9. Thus, the conductive particles in the anisotropic conductive material 9 can be crushed to ensure electrical connection.

[0039]

According to the present invention, an aluminum external terminal portion is covered with a protective film of lead oxide glass having excellent moisture impermeability and is protected from protrusion of an anisotropic conductive material used for connection to an external cable. As a result, aluminum corrosion of the external terminal portion of the connection portion was eliminated.

The present invention also relates to a fluorescent display tube in which a large number of external terminals made of an aluminum thin film are often connected to an external cable with an anisotropic conductive material.
It is particularly useful in that high connection reliability can be maintained without causing wiring corrosion even when operated in a high temperature and high humidity environment.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along a cutting line (A)-(A) of FIG.

FIG. 3 is a cross-sectional view showing a connection step in one example of the embodiment of the present invention.

FIG. 4 is a sectional view showing an example of a conventional connection structure between a fluorescent display tube and an external cable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluorescent display tube 3 Anode substrate as a board 4 Wiring conductor 5 External terminal part as an aluminum wiring 6 Cross layer 7 Protective film 8 Flexible cable as a connected object or connection wiring 9 Anisotropic conductive material 9a Anisotropic conductive material 20 Thermocompression bonding device 23 Silicon sheet as pressing material

Claims (5)

[Claims] 1. A connection structure of an aluminum wiring for connecting an aluminum wiring formed on a substrate and a connected body outside the substrate using an anisotropic conductive material, wherein the aluminum wiring and the connected body are connected to each other. The aluminum wiring not facing the connected body at least in the vicinity of the connected body so that the anisotropic conductive material protruding from between does not contact the aluminum wiring not facing the connected body. A connection structure for aluminum wiring, which is covered with a protective film. 2. A connection structure of an aluminum wiring connecting an aluminum wiring formed on a substrate of a fluorescent display tube and a connection wiring outside the fluorescent display tube by using an anisotropic conductive material, wherein: The aluminum not facing the connection wiring at least in the vicinity of the connection wiring so that the anisotropic conductive material protruding from between the connection wiring does not contact the aluminum wiring not facing the connected object. A connection structure for aluminum wiring, wherein the wiring is covered with a protective film. 3. The connection structure for aluminum wiring according to claim 1, wherein said protective film is made of lead oxide glass. 4. The method according to claim 1, wherein the anisotropic conductive material is an epoxy adhesive containing a large number of fine conductive particles.
The connection structure of the described aluminum wiring. 5. An aluminum wiring connection method for connecting an aluminum wiring covered with a protective film to a part to be connected using an anisotropic conductive material, except for an end portion, the end of the part being connected with the anisotropic conductive material interposed therebetween. Part of the aluminum wiring and a part of the protective film is overlapped with the end of the aluminum wiring, and the end of the connected body is pressed while being heated with an elastic pressing material thicker than the thickness of the protective film. Connection method.